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+# Scalar - an opinionated repository management tool
+
+Scalar is an add-on to Git that helps users take advantage of advanced
+performance features in Git. Originally implemented in C# using .NET Core,
+based on the learnings from the VFS for Git project, most of the techniques
+developed by the Scalar project have been integrated into core Git already:
+
+* partial clone,
+* commit graphs,
+* multi-pack index,
+* sparse checkout (cone mode),
+* scheduled background maintenance,
+* etc
+
+This directory contains the remaining parts of Scalar that are not (yet) in
+core Git.
+
+## Roadmap
+
+The idea is to populate this directory via incremental patch series and
+eventually move to a top-level directory next to `gitk-git/` and to `git-gui/`. The
+current plan involves the following patch series:
+
+- `scalar-the-beginning`: The initial patch series which sets up
+ `contrib/scalar/` and populates it with a minimal `scalar` command that
+ demonstrates the fundamental ideas.
+
+- `scalar-c-and-C`: The `scalar` command learns about two options that can be
+ specified before the command, `-c <key>=<value>` and `-C <directory>`.
+
+- `scalar-diagnose`: The `scalar` command is taught the `diagnose` subcommand.
+
+- `scalar-and-builtin-fsmonitor`: The built-in FSMonitor is enabled in `scalar
+ register` and in `scalar clone`, for an enormous performance boost when
+ working in large worktrees. This patch series necessarily depends on Jeff
+ Hostetler's FSMonitor patch series to be integrated into Git.
+
+- `scalar-gentler-config-locking`: Scalar enlistments are registered in the
+ user's Git config. This usually does not represent any problem because it is
+ rare for a user to register an enlistment. However, in Scalar's functional
+ tests, Scalar enlistments are created galore, and in parallel, which can lead
+ to lock contention. This patch series works around that problem by re-trying
+ to lock the config file in a gentle fashion.
+
+- `scalar-extra-docs`: Add some extensive documentation that has been written
+ in the original Scalar project (all subject to discussion, of course).
+
+- `optionally-install-scalar`: Now that Scalar is feature (and documentation)
+ complete and is verified in CI builds, let's offer to install it.
+
+- `move-scalar-to-toplevel`: Now that Scalar is complete, let's move it next to
+ `gitk-git/` and to `git-gui/`, making it a top-level command.
+
+The following two patch series exist in Microsoft's fork of Git and are
+publicly available. There is no current plan to upstream them, not because I
+want to withhold these patches, but because I don't think the Git community is
+interested in these patches.
+
+There are some interesting ideas there, but the implementation is too specific
+to Azure Repos and/or VFS for Git to be of much help in general (and also: my
+colleagues tried to upstream some patches already and the enthusiasm for
+integrating things related to Azure Repos and VFS for Git can be summarized in
+very, very few words).
+
+These still exist mainly because the GVFS protocol is what Azure Repos has
+instead of partial clone, while Git is focused on improving partial clone:
+
+- `scalar-with-gvfs`: The primary purpose of this patch series is to support
+ existing Scalar users whose repositories are hosted in Azure Repos (which
+ does not support Git's partial clones, but supports its predecessor, the GVFS
+ protocol, which is used by Scalar to emulate the partial clone).
+
+ Since the GVFS protocol will never be supported by core Git, this patch
+ series will remain in Microsoft's fork of Git.
+
+- `run-scalar-functional-tests`: The Scalar project developed a quite
+ comprehensive set of integration tests (or, "Functional Tests"). They are the
+ sole remaining part of the original C#-based Scalar project, and this patch
+ adds a GitHub workflow that runs them all.
+
+ Since the tests partially depend on features that are only provided in the
+ `scalar-with-gvfs` patch series, this patch cannot be upstreamed.